1. PSYCHOLOGY
UNIT 3
STAGES OF SLEEP

2. Please take notes on the following underlined information...

3. STAGE ONE
Stage 1 is the beginning of the sleep cycle, and is a relatively light stage of sleep.

4. Stage 1 can be considered a transition period between wakefulness and sleep.

5. In Stage 1, the brain produces high amplitude theta waves, which are very slow brain waves.

6. This period of sleep lasts only a brief time (around 5-10 minutes), and if you awaken someone in the stage, they might report that they weren't really asleep.

7. STAGE TWO
Stage 2 is the second stage of sleep and lasts for approximately 20 minutes.

8. The brain begins to produce bursts of rapid, rhythmic brain wave activity known as sleep spindles.

9. Body temperature starts to decrease and heart rate begins to slow.

10. STAGSTAGE THREE THREE
Deep, slow brain waves known as delta waves begin to emerge during stage 3 sleep.

11. Stage 3 is a transitional period between light sleep and a very deep sleep.

12. STAGE FOUR
Stage 4 is sometimes referred to as delta sleep because of the slow brain waves known as delta waves that occur during this time.

13. Stage 4 is a deep sleep that lasts for approximately 30 minutes.

14. Bed-wetting and sleepwalking usually occur at the end of stage 4 sleep.

15. STAGE FIVE
Most dreaming occurs during the fifth stage of sleep, known as rapid eye movement (REM) sleep.

16. REM sleep is characterised by eye movement, increased respiration rate, increased brain activity.

17. REM sleep is also referred to as paradoxical sleep because while the brain and other body systems become more active muscles become more relaxed.

18. Dreaming occurs because of increased brain activity, but voluntary muscles become paralysed.

19. Sleep does NOT progress through these stages in sequence, however.

20. Sleep begins in stage 1 and progresses into stages 2, 3, and 4.
After stage 4 sleep, stage 3 and then stage 2 sleep are repeated before entering REM sleep.

21. Once REM sleep is over, the body usually returns to stage 2 sleep

22. Sleep cycles through these stages approximately 4 or 5 times throughout the night.

23. On average, we enter the REM stage approximately 90 minutes after falling asleep.

24. The first cycle of REM sleep might last only a short amount of time, but each cycle becomes longer, so REM sleep can last up to an hour as sleep progresses.

25. THE END